The conventional power amplification device with a high efficiency includes a Doherty amplifier that combines a carrier amplifier with a peak amplifier (for example, refer to Non-Patent Document 1). The carrier amplifier is used to ensure linearity when an input signal is smaller (hereinafter, referred to as “at the time of the smaller signal”), and the peak amplifier is used to ensure a saturated electric power when the input signal is larger (hereinafter, referred to as “at the time of the larger signal”). The input signal that has been input to the Doherty amplifier is divided into two signals one of which is input to the carrier amplifier, and another of which is input to the peak amplifier. The carrier amplifier is normally biased from class A to class AB or to class B, and therefore executes amplification and output irrespective of the level of the input signal. The peak amplifier is normally biased to class C, and therefore becomes in a non-operating state at the time of the smaller signal and becomes in an operating state at the time of the larger signal to amplify and output the signal. That is, at the time of the smaller signal, only the carrier amplifier operates, and hence the highly efficient operation is obtained, and at the time of the larger signal, the outputs of the carrier amplifier and the peak amplifier are combined together, and hence a highly saturated electric power is ensured.
Non-Patent Document 1: Masatoshi Nakayama, Tadashi Takagi, “Techniques for Low Distortion and High Efficiency Power Amplifiers”, MW E2004 Microwave Workshops Digest. P575-584